‘ of the

Medical Researeh Council

MICROBIAL GENETICS RESEARCH UNIT
| Hammersmith Hospital,

Ducane Road,

” a

Tondon, W.12.

*

WH/rr 3rd December, 1957.

Professor J. Isderberg,
Dept. of Genetics,

Genetics Building,

Sehool of Medicine,

The University of Wisconsin,
Madison 6,

Wisconsin, U.S.A.

Dear Josh,

I find I have on my file at least three unanswered letters from you, one from
Madison sand two from Australia. Please accept my most humble apologies for not
writing to you before, but as you know, I had an extended holiday this year during
which I ceased even to think, which has been followed by a rather busy return to
reality when I have been spending all my time with architects and catalogues of
equipment in connection with my new unit, which should be properly housed about a
year from now.

Many thanks for the typescript of your paper on "pedigrees of zygoteisolates”.
I have sent this on te-Paris as you asked. I found it very,interesting but it.is
too complicated to discuss in detail in this letter. I do/think, though, that
there is any real evidence in favour of regiprosity among recombinants issuing from
a single zygote. I do not think that this will, in fact, be found; however you hawe
provided some evidence which might tie up normal segregation rather neatly with some
[as your diploids - I refer specifically to the problem of the
homozygosity for markers in which the two parents differ.

I was interested in your work on the question of the dominance of Az” in your
diploids and I am glad that you were able to confirm the fact that on minimal mediun,
Az™ appears to be dominant, though it is interesting that the reverse should seem
to hold on nutrient agar. As I have indicated, I have had no time since my return
to do any bench work and I am rather keen to make a start on something quite
different from Kl2, at least as the principle line of research. Just what this will
be I am not abso lutely certain, but I have a hankering after diphasic variation, an
interest in which brought me into genetics in the first place. At least, thanks to
you, I have something to go on.

I expect you had a wonderful time in Australia. I had a letter from Holleway

/over
<——— 204 Plog 185%] ——>

who seems to have greatly enjoyed and got much value from your visit. Incidentally,
I was very interested to see an abstract of a paper by Allan Richter recently. It
certainly looks as if when the Hfr loQus is present on the - Ceiromo some that F goes to
it. I-am coming round to the view that.F may well be a ikSplasmic factor. Iam
rather keen on the idea, suggested to me by Gunther Stent x long time ago, that F
may really be the vegetative stage of something hot unlike a defective temperate _
phage. .

_* v
I am sorry to say that for various reasons I will not be going: to. Stockholm
next August, but will probably meet you and I hope Esther, at Royaumont. I hope,
though, that you will find it possible to visit Iondon for sometime on your way back
to America. We now have a new house and would be delighted to put you both up.
Please give my best wishes to Usther.

Yours,

‘

a. Hayes.